Retractable undercarriages



June 8, 1965 J. PERDU E ETAL 3,

RETRACTABLE UNDERCARRIAGES Filed May 25, 1964 7 Sheets-Sheet 1 FIG. 7

June 8, 1965 J. PERDUE ETAL 3,183,025

RETRACTABLE UNDERCARRIAGES Filed May 25, 1964 7 Sheets-Sheet 2 Fl G. 3.

June 8, 1965 J. PERDUE ETAL 3,188,026

RETRACTABLE UNDERCARRIAGES Filed May 25, 1964 7 Sheets-Sheet 3 J. PERDUE ETAL RETRACTABLE UNDERCARRIAGES June 8, 1965 7 Sheets-Sheet 4 Filed May 25, 1964 June 8, 1965 Filed May 25, 1964 7 Sheets-Sheet 5 L .JU'

June 8, 1965 Filed May 25, 1964 J. PERDUE ETAL RETRACTABLE UNDERCARRIAGES 7 Sheets-Sheet 6 FIG.9

June 8, 1965 Filed May 25, 1964 J. PERDUE ETAL RETRACTABLE UNDERCARRIAGES 7 Sheets-Sheet '7 United States Patent 3,188,026 RETRACTABLE UNDERCARRIAGES Jack Perdue, Great Sanlre'y, Warrington, and Arthur Cecil Aitchison, Liverpool, England, assignors' to Electro- Hydraulics Limited, Warrington, England, a corporation of the United Kingdom Filed May 25, 1964, Ser. No. 369,878 Claims priority, application Great Britain, May 30, 1963,

21,758/ 63 9 Claims. (Cl. 244-102) This invention is concerned with retnactable undercarriages for aircraft.

An undercarriage is known comprising an inboard and an outboard wheel, in which the inboard wheel is mounted on an inner leg having a pivotal axis transverse the aircraft and the outboard wheel is mounted on an outer leg having a pivotal axis fore and aft with respect to the aircraft, the legs being connected by a pivotal link, a single retraction jack acting to retract the inboard wheel vertically, and, through the connecting link, to fold the outboard wheel inwardly through 90.

This construction has several disadvantages which include structural difficulties on the'aircraft in providing a well braced attachment for the fore and aft pivot where vertical drag and side loads as well as torque have to be taken off, due to the pivot point being situated a long way out from the side of the fuselage. This would result in a heavy. structure.

Also, the off-set of the connecting link about the fore and aft pivot is sm alland therefore does not provide a very good side bracing member for transmitting sideloads from the outer leg' to the inner leg.

Wheel changing, especially on military aeroplanes,

should be a simple operation and there is a seriousdisadvantage in the known arrangement when this aspect is considered. To remove the inner wheel fromits axle the connecting link must be disconnected at one end and the outer wheel assembly rotated out of the way to provide withdrawal space for the inner tyre and wheel. This may also mean that after the inner Wheel and tyre has been replaced and the connecting link re-assenibled, retraction tests might be necessary to check the retraction mechanism of which the connecting linkis part. This may also mean using the largemain aircraft jack for wheel changing instead of a small one which is normal practice.

These disadvantages are overcome by the retractable undercarriage constructed according to this invention.

According to the present invention a retractable undercarriage for aircraft comprises a beam, at least one pair of wheels consisting of an inboard and an outboard wheel, each wheel being mounted respectively on a mounting v member for pivotal movement relative to the beam, which is hingedly connected to the aircraft about an axis parallelthereto, and means for retracting and lowering the undercarriage, the arrangement being such that, on retraction, the beam is pivoted from a substantially horizontal position to a. substantially vertical position, thereby causing each inboard wheel to swing downwards and inwards into a substantially horizontal position and each outboard wheel to swing upwards and inwards into a substantially vertical position.

In the preferred form of construction two inboard and two outboard wheels .are provided, each associated with a mounting member, for which purpose first links are pivot- .ally connected between the mounting members associated :with the outboard wheels and a fixed point for each on the aircraft, and second links are pivot-ally connected between the mounting members associated with the inboard wheels and a fixed point on the aircraft, the arrangement being such that when the aircraft. is static on the ground,

each outboard wheel, imparts a compressive load and each inboard wheel a tensile load, to its respective link.

In an alternative construction, the first links are pivotally connected between the mounting members associated with the inboard Wheels and a fixed point for each on the aircraft, and the second links are coupled between the mounting members associated with the inboard and outboard wheels, the arrangement being such that, when th aircraft is static on the ground, the said wheels impart a tensile load to their respective links.

Again the first links may be pivotally connected between the mounting members associated with the outboard wheels and a fixed point for each on the aircraft, and the second links pivo-tally connected between the inboard wheel mounting members and the outboard Wheel mounting members, so that when the aircraft is static on the ground, both wheels imp-art a compressive load to their respective links.

'In each of the above constructions, the mounting mem- [bars are pivotally connected to the beam about axes substantially fore and aft with respect to the aircraft, and means are provided for raising and lowering the beam, and for locloing the undercarriage in its raised and lowered positions. These undercarriage down and/or up locks may be incorporated in the retraction motor in a known manner.

Again, in each of the above constructions, the arrangemom is such that, on retraction, the said first and second links act to rotate the associated mounting members so that each outboard wheel is stowed substantially in a vertical plane and each inboard wheel substantially in a horizontal plane. I

The invention will now .be described with reference to the accompanying drawing FIGURES l-11 in which:

- FIGURE 1 is a rear end elevation of a preferred form of construction in which .the first and sec-0nd links are pivotally connected to the aircraft, the undercarriage being shown in the lowered free in air position;

FIGURE 2 shows the undercarriage of FIGURE l'in the retracted position, the retraction motor being omitted for clarity;

FIGURE 3 is a rear end elevation of a further form of i undercarriage in which one of the links is pivoted to the aircraft and the other is connected between the mounting members, the undercarriage being shown in the lowered free in air position;

FIGURE 4 shows the undercarriage of FIGURE 3 in the retracted position, the retraction motor being omitted for clarity;

FIGURE 5 is a rear end elevation of a further alien native construction, the undercarriage being shown in the lowered free in air position;

FIGURE 6 shows the undercarriage of FIGURE 5 in the retracted position, the retraction motor being omitted for clarity;

FIGURES 7 and 8 are respectively a side and rear elevation of an undercarriage according to-FIGURE 1;

FIGURE 9 is a plan view of the undercarriage of FIG- URES 7 and 8;

FIGURE 10 is a rear end elevation of a further alternative construction, the undercarriage being shown in the lowered free in air position, theretraction motor being omitted;

FIGURE ll shows the undercarriage of FIGURE 10 in the retracted position.

In the drawing, FIGURES 1 to 6 and 10 and 11 are diagrammatic representations of trailing link type undercarriages according to this invention. The-same numerals are used to identify similar parts in these figures.

Referring to FIGURES l and 2, a beam 1 is pivotally mounted at 2 to a fixed point on the aircraft for pivotal movement transverse of the aircraft. An hydraulic jack 3 all 7 3 is pivotally connected between a point 4 on beam 1 and a fixed point 5 on the aircraft. An inboard wheel 6 is mounted for rotation on an axle (not shown) which axle is mounted-on a trailing link (not shown) pivoted to a mounting member 7. Movement of the wheel 6 with respect to the mounting member 7 is controlled by a shock absorber (not shown). A centre line 8 indicates the position of the wheel axle. The mounting member 7 is pivoted on the beam 1 at 9, the pivotal axis being substantially in the fore and aft direction with respect to the aircraft. An outboard wheel 10 is similarly mounted for rotation about an axle, whose position is indicated by a centre line 11, which axle is supported on a trailing link (not shown) pivotally mounted on a mounting member 12. A shock absorber (not shown) arranged between the trailing link and the mounting member 12 controls the movement of the wheel 10. The mounting member 12 is pivoted to the beam 1 at 13, the pivot pin lying substantially fore and aft with respect to the aircraft. A link 14 is pivotally connected between the point 5 on the aircraft and a point 15a on an arm 15 of the mounting member 7. A further link 16 is pivotally connected between a fixed point 17 on the aircraft and a point 13a on an arm 18 of the mounting member 12.

In FIGURE 1, the undercarriage is shown in the lowered free in air position and is locked in this position by e.g. a mechanical lock in the hydraulic jack 3. When the hydraulic jack 3 is unlocked and extended, the beam 1 is rotated into the position shown in FIGURE 2. The links 44 and 16 are so arranged as to rotate the wheels 6 and 10 in the vertical plane in a direction contrary to the direction of movement of the beam 1. Thus, the beam 1, in going from the posit-ion of FIGURE 1 to the position of FIGURE 2, rotates in a clockwise direction about the point 2. During this movement, the links 14 and 16 rotate the wheels 6 and 10 in an anticlockwise direction about the points 9 and 13 respectively so that the wheel 10 is retracted into a position which is substantially in the vertical plane and parallel to the contour of the aircraft fuselage, whilst the wheel 6 is retracted into a position substantially in the horizontal plane. Broken lines indicate the fuselage contour and retraction space for the undercarriage.

Referring back to FIGURE 1 it will be seen that when the aircraft is static on the ground the loads on the wheels 6 and 10 are such as to impart a tensile load in the link 14 and a compressive load in the link 16. The geometry is preferably arranged such that the moments about the point 2 of the forces in the links 14 and 16 substantially counteract at least part of the moments about the point 2 of the loads on the wheels, thereby alleviating the load on the undercarriage down lock. In this way a relatively small and lightly loaded undercarriages down lock can be used. In this way weight and space can be saved and the inherent reliability of a relatively lightly loaded lock can be obtained. The undercarriage may be locked in the UP position by a further mechanical lock in the hydraulic jack 3 or alternatively by other known locking means arranged between the undercarriage and the aircraft.

Referring to FIGURES 3 and 4, the link 14 is pivotally connected between the point 15a on the arm 15 of the mounting member 7 and a fixed point 2.0 on the aircraft. The mounting member 7 is pivoted on the beam 1 at the point 4 which also forms a pivotal attachment between the hydraulic jack 3 and the beam 1. The link 16 is pivotally connected between the point 1811 on the ar m18 of the mounting member 12 and the point 15a on the arm 15 of the mounting member 7. The undercarriage down lock and up lock may again be incorporated in the hydraulic jack 3, or separate locks may be provided. The hydraulic jack 3 is extended to rot-ate the beam 1 from the lowered position shown in FIGURE 3 to the retracted position shown in FIGURE 4. As before, the links 14 and 16 act to rotate the wheels 6 and 10 anticlockwise about the points 4 and 13 respectively, so that the wheel 10 is stowed in substantially the vertical plane whilst the wheel 6 is stowed in substantially the horizontal plane.

It will be seen that, in this construction also, when the aircraft is static on the ground the moment of the forces in the link 14 about the point 2 can be arranged so as to counteract at least part of the moment of the loads on the wheels about the point 2, thus alleviating the down lock loads. A vertical load on the outboard wheel, or wheels, will produce a tensile load in the link 16 which adds to the tensile load produced in the link 14 by a vertical load on the inboard wheel, or wheels. This load in the link 14 will produce a moment about the point 2 in an anticlockwise direction in opposition to the clockwise moment about point 2 produced by the vertical loads acting on the outboard and inboard wheels. By a suitable choice of geometrical offsets the opposing moments can be adjusted to reduce the static down lock load to zero, or to a low tension or compression value.

Referring to FIGURES 5 and 6, the link 16 is now pivotally connected between the point 18a on the arm 18 of mounting member 12 and a point 190 of an arm 19 on the mounting member 7. Thus the undercarriage in this case is connected to the aircraft at two points, 2 and 5, as com-pared with three points 2, 5 and 17 in FIGURES l and 2. The undercarriage down lock may again be incorporated in the hydraulic jack 3, as also may be the undercarriage up lock. The hydraulic jack 3 is extended to raise the undercarriage from the position shown in FIGURE 5 to that shown in FIGURE 6. The hydraulic jack 3 is omitted from FIGURE 6 for clarity. As before, the links 14 and 16 act to rotate the wheels 6 and 10 anti-clockwise about the pivots 9 and 13 so that the wheel 10 is stowed in the substantially vertical plane, whilst the wheel 6 is stowed in the substantially horizontal plane.

Referring now to FIGURES l0 and 11, the link 14 in this case is pivotally connected between the point 18a on the arm 18 of the mounting member 12 and a fixed point 5 on the aircraft. In this construction, however, the link 16 is pivotally connected between the point 15a on the arm 15 of the mounting member 7, and a point 28a provided on a further arm 28 of the mounting member 12 associated with the outer wheel 10. The undercarriage down lock may again be incorporated in the hydraulic jack 3, as also may be the undercarriage up lock. The hydraulic jack 3 (not shown) is extended to raise the undercarriage from the position shown in FIGURE 10 to that shown in FIGURE 11. As before, the links 14 and 16 act to rotate the wheels 6 and 10 anti-clockwise about the pivots 9 and 13 so that the wheel 10 is stowed in the substantially vertical plane, whilst the wheel 6 is stowed in the substantially horizontal plane.

It will be appreciated that constructions other than those illustrated can be used. For instance, in FIGURES 3 and 5, the arm 18 of the mounting member 12 may be bent through substantially thereby causing the link 16 to be in compression instead of tension. It will also be appreciated that the wheels need not necessarily .be arranged to be rotated by the links in a direction counter to that of the beam. For example, the outboard wheel or wheels may be rotated so that in the retracted position they lie between the beam and the fuselage contour.

FIGURES 7 and 8 illustrate an undercarriage for an aircraft of the type illustrated diagrammatically in FIG- URES 1 and 2. Similar parts are identified with the same numerals. The undercarriage of FIGURES 7 and 8 has two outboard wheels 10, 10a and two inboard wheels 6 and 6a, of which 6only is shown. The wheels 6 and 10 are supported on trailing links and the wheels 6a, 1012 are supported on leading links. A separate shock absorber is provided to control the movement of each wheel. FIGURE 7 shows a trailing link 21 for the wheel 10 pivoted at 22 to the mounting member 12. The trailing link 21 carries an axle 23 on which the wheel 10 is mounted at its rear end. An arm 24 is secured to the link 21 and a shock absorber 25 is pivotally connected between the arm 24 and the mounting member 12. A brake torque link 27 is pivotally connected between a wheel brake plate 26 and the mounting member 12. The arrangement just described is duplicated for the wheel a, whose axle 23a is mounted on the forward end of a leading link 21a which is pivoted at its rear end to the mounting member 12a at 22a. The mounting members 12, 12a 7 are both secured to the pivot pin 13. A shock absorber 25a is pivotally connected between the mounting member 12a and an arm 24a attached to the leading link 21a. A brake torque link 27a is pivotally connected between a wheel brake plate 26a and the mounting member 12a. The links 14a and 16a are connected to fixed points 5a (not shown) and 17a on the aircraft.

The inboard wheels 6, 6a are similarly provided with trailing and leading links, shock absorber, and brake torque links as for the outboard wheels. The under carriage down lock (not shown) comprises a mechanical lock of known type incorporated in the hydraulic jack 3.

The undercarriage is retracted in the manner described with reference to FIGURE 1. a

What we claim is:

1. A retractable undercarriage for aircraft comprising a beam for pivotal connection to a fixed point on the aircraft for pivoting movement transverse the aircraft, means for raising and lowering the beam, means to lock the undercarriage in its raised and lowered positions, at least one inboard wheel, at least one outboard wheel, each said wheel being supported by a mounting member, said mounting members being pivotally mounted on the beam, the pivotal axes being substantially fore and aft with respect to the aircraft, at least one first link pivotally connected between the mounting member associated with an outboard wheel and a fixed point on the aircraft, at least one second link pivotally connected between the mounting member associated with an inboard wheel and a fixed point on the aircraft, the outboard wheel, when the aircraft is static on the ground, imparting a compressive load, the inboard wheel a tensile load, to their respective links, the arrangement being such that on retraction, the said first and second links act to rotate 'the associated mounting members so that the outboard wheel is stowed substantially in a vertical plane and the inboard wheel substantially in a horizontal plane.

2. A retractable undercarriage for aircraft comprising a beam for pivotal connection to a fixed point on the aircraft for pivoting movement transverse the aircraft, means for raising and lowering the beam, means to lock the undercarriage in its raised and lowered positions, at least one inboard wheel, at least one outboard wheel, each said wheel being supported by a mounting member, said mounting members being pivotally mounted on the beam, the pivotal axes being substantially fore and aft with respect to the aircraft, at least one first link pivotally connected between the mounting member associated with the inboard wheel and a fixedpoint on the aircraft, at least one second link coupled between the mounting members associated with both inboard and outboard'wheels, the said wheels, when the aircraft is static on the ground, imparting a tension load to their respective links, the arrangement being such that on retraction, the said first and second links act to rotate the associated mounting members so that the outboard wheel is stowed substantially in a vertical plane and the inboard Wheel substantially in a horizontal plane.

3. A retractable undercarriage for aircraft comprising a beam for pivotal connection to a fixed point on the aircraft for pivoting movement transverse the aircraft, means for raising and lowering the beam, means to lock the undercarriage in its raised and lowered positions, at least one inboard wheel, at least one outboard wheel, each said wheel being supported by a mounting member, said mounting members being pivotally mounted on the beam, the pivotal axes being substantially fore and aft with respect to the aircraft, at least one first link pivotally connected between the mounting member associated with an outboard wheel and a fixed point on the aircraft, at least one-second link pivotally connected between an inboard wheel mounting member and the outboard wheel mounting member both wheels, when the aircraft is static on the ground, imparting a compressive load, to their respective links, the arrangement being such that on retraction the said first and second links act to rotate the associated mounting members so that the outboard wheel is stowed substantially in a vertical plane and the inboard wheel substantially in a horizontal plane.

4. A retractable undercarriage construction for aircraft comprising frame means; a beam; means mounting said beam on said frame means for rocking movements about an axis; inboard wheel journaling means; outboard wheel journaling means; means mounting the respective journaling means on said beam for rocking movements relative to said beam about axes substantially parallel to said axis; linkage means interconnecting said frame means and the means mounting the respective journaling means for rocking the mounting means relatively to said beam in response to rocking of the latter; and power operated means connected to the frame means and acting on the beam for rocking the latter about said axis to raise and lower said undercarriage.

5. The construction set forth in claim 4 wherein said linkage means comprises a first link extending between said frame means and one of said mounting means and a second link extending between said frame means and the other of said mounting means.

6. The construction set forth in claim 5 wherein the arrangement of said links is such that when said undercarriage is in its lower position one of said links may be stressed in tension and the other of said links may be stressed in compression.

7. The construction set forth in claim 4 wherein said linkage means comprises a first link extending between said frame means and one of said mounting means; and a second link extending between both of said mounting means. i

8. The construction set forth in claim 7 wherein the arrangement of said links is such that when said undercarriage is in its lower position one of said links may be stressed in tension and the other of said links may be stressed in compression.

9. The construction set forth in claim 7 wherein the arrangement of said links is such that when said undercarriage is in its lower position both of said links may be a stressed in tension.

FERGUS S. MIDDLETON, Primary Examiner. MILTON BUCHLER, Examiner. 

3. A RETRACTABLE UNDERCARRIAGE FOR AIRCRAFT COMPRISING A BEAM FOR PIVOTAL CONNECTION TO A FIXED POINT ON THE AIRCRAFT FOR PIVOTING MOVEMENT TRANSVERSE THE AIRCRAFT, MEANS FOR RAISING AND LOWERING THE BEAM, MEANS TO LOCK THE UNDERCARRIAGE IN ITS RAISED AND LOWERED POSITIONS, AT LEAST ONE INBOARD WHEEL, AT LEAST ONE OUTBOARD WHEEL, EACH SAID WHEEL BEING SUPPORTED BY A MOUNTING MEMBER, SAID MOUNTING MEMBERS BEING PIVOTALLY MOUNTED ON THE BEAM, THE PIVOTAL AXES BEING SUBSTANTIALLY FORE AND AFT WITH RESPECT TO THE AIRCRAFT, AT LEAST ONE FIRST LINK PIVOTALLY CONNECTED BETWEEN THE MOUNTING MEMBER ASSOCIATED WITH AN OUTBOARD WHEEL ND A FIXED POINT ON THE AIRCRAFT, AT LEAST OEN SECOND LINK PIVOTALLY CONNECTED BETWEEN AN INBOARD WHEEL MOUNTING MEMBER AND THE OUTBOARD WHEEL MOUNTING MEMBER BOTH WHEELS, WHEN THE AIRCRAFT IS STATIC ON THE GROUND, IMPARTING A COMPRESSIVE LOAD, TO THEIR RESPECTIVE LINKS, THE ARRANGEMENT BEING SUCH THAT ON RETRACTION THE SAID FIRST AND SECOND LINKS ACT TO ROTATE THE ASSOCIATED MOUNTING MEMBERS SO THAT THE OUTBOARD WHEEL IS STOWED SUBSTANTIALLY IN A VERTICAL PLANE AND THE INBOARD WHEEL SUBSTANTIALLY IN A HORIZONTAL PLANE. 